#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int run(int x)
{
	if (x <=2)
		return 1;
	else
	{
		return run(x- 1) + run(x - 2);
	}
}
int main()
{
	int n = 0;
	int m = 0;
	scanf("%d", &n);
	m=run(n);
	printf("%d", m);

	return 0;
}